Manufacturers of precision components must produce parts fast and economically in order to survive in a competitive marketplace. To this extent, manufacturers rely upon automated technology such as robotics for welding, lasers for cutting, numerical controlled machine tools for crafting, and the like. These devices all possess the ability to perform a variety of functions accurately, quickly and with infinite repeatability. Numerical controlled machine tools, or CNC machines, exemplify this ability. Conventional CNC machines utilize a variety of tools of which any tool can be accessed quickly and placed within a thousandth of an inch of a preprogrammed placement point. This accuracy, coupled with its repeatability, allows a manufacturer to produce precision components quickly and economically.
Computers have made these precision machines possible by controlling the complexities of machining through a series of preprogrammed instructions. However, while computers significantly increase machining speed, accuracy and repeatability, machining set-up remains dependent upon human placement of the workpiece. Thus, accuracy is dependent upon proper placement of the workpiece within tolerances that meet or exceed the tolerance capability of the machine. Once a set of computer instructions or "program" is in place, it is essential that the component "workpiece" be placed within the coordinates of the preprogrammed instructions. This set-up must be done quickly and accurately for a machine that is not running defeats a primary purpose of a computer controlled machine.
The use of pallets have become an industry standard among manufacturers of precision machined components. A workpiece, or more likely multiple workpieces, are secured to a pallet external of the machine and slid onto a predetermined location when the machine is available. The use of a pallet simply allows the workpiece(s) of any shape to be attached thereto separate from the machine itself and the pallet provides a uniform means of securing itself to the machine. While a workpiece is being machined, another pallet can be prepared and slid into position upon demand. The pallet typically employs a critical datum point which is designed for alignment to the machine. Thus, if multiple workpieces are positioned upon a pallet, alignment of the pallet results in alignment of all items secured thereto. Once the pallet is aligned, machine operation can be started per its programmed instructions and the operator is free to set up another pallet.
While transfer of a pallet from a remote location may reduce the amount of time a machine is idle, the means used for transfer of the pallet creates an additional problem, namely, obstruction of the working area in front of the machine. For example, once a pallet is set-up at a remote location the pallet is transferred to the operating machine by fork lift, crane, or by a means allowing for the sliding of the pallet from a remote location to the machine's operating section. Typically the latter mode of transfer is utilized by placement of a span of metal bridging one location to another. This "bridge" is used to slide the pallet over any distance by use of rollers placed onto the bridge. However, due to the size and weight of pallets bridges must be large enough to provide stability as well as strong, the combination creating an obstacle in and of itself. For example, U.S. Pat. No. 4,915,569 issued Apr. 10, 1990 to Cherko illustrates a swivel frame type bridge which permits movement of pallets from a location separate to the machine directly onto the machine. While the Cherko device assists the operator in placement of pallets onto a machine, access is severely limited by the size of the device despite the use of an horizontal articulating mechanism.
While the use of a bridge greatly benefits an operator in the transport of heavy pallets, it should be obvious that any apparatus mounted directly in front of a machine severely limits access to the machine. Access is necessary for tool changing, service, pallet alignment, cleaning, oiling, adjusting, supervising, and so forth. These problems are further expounded upon by recent OSHA requirements that the sides of such machines be enclosed by a stationary shield which, when used in combination with a fixed bridge, nearly eliminates access by the operator to the operating area.
My invention is specifically designed to overcome the aforementioned problems by use of a movable bridge having all the inherent qualities found in a fixed bridge. Therefore, it is the effective resolution of these problems that the present invention is directed.